In letters delivered Sunday, Israel says the migrants have 60 days to accept the offer to leave the country for an unnamed African destination in exchange for $3,500 and a plane ticket. Those who don’t by April 1 will be incarcerated indefinitely.

Some 40,000 migrants, nearly all from Eritrea and Sudan, fled danger for the safety and opportunities of Israel in recent years. Many have expressed fear of being sent to Rwanda, their likely destination.

The deportation plan has sparked outrage in Israel, where groups of pilots, doctors, writers, rabbis and Holocaust survivors have appealed to have it halted. They say the deportations are unethical and would damage Israel’s image as a refuge for Jewish migrants.

Meanwhile, Israel’s prime minister says it will legalize an isolated West Bank outpost in response to the murder of one of its residents.

Prime Minister Benjamin Netanyahu told his weekly Cabinet meeting on Sunday that those who try to “break our spirit and weaken us made a grave mistake.” He says his government will legalize Havat Gilad to “allow the continuing of normal life there.”

Earlier this month, Havat Gilad resident Rabbi Raziel Shevah, a 35-year-old father of six, was shot dead from a passing vehicle as he drove near his home in the unauthorized settlement outpost near Nablus.

The community of a few hundred Israelis is located deep inside the West Bank.

The anti-settlement Peace Now group says the effort to legalize it is a “cynical exploitation of the murder.”